Tag: black holes

No, you can’t see a black hole. What you might be able to see, though, is the way in which relativity predicts a spinning black hole will bend space, time, and light around it. Scientists say in a new study in Nature Physics that they are closer than ever to being able to see this effect in faraway black holes from our vantage point here on Earth.

Galaxies probably have spinning, supermassive black holes at their center, and spinning black holes possess two types of angular momentum, study coauthor Bo Thide explains. There’s spin angular momentum, which is analogous to what the Earth creates as it spins on its axis, and there’s orbital angular momentum, which is analogous to what the Earth creates as it orbits the sun. Thidé says that the second effect—orbital angular momentum—distorts light in a way that scientists who know what to look for might be able to see it from here.

“Around a spinning black hole, space and time behave in such an odd way; space becomes time, time becomes space, and the whole space-time is actually dragged around the black hole, becomes twisted around the black hole,” Professor Thidé explained. “If you have radiation source… it will then sense this twisting of spacetime itself. The light ray may think that ‘I’m propagating in a straight line’, but if you look at it from the outside, you see it’s propagating along a spiral line. That’s relativity for you.” [BBC News]

One of these things is not like the other: Astronomers have spotted a dwarf galaxy that spans just 3,000 light years across (as opposed to our Milky Way’s diameter of 100,000 light years), but hosts an outsize supermassive black hole for its puny size.

Some smaller galaxies have supermassive black holes as well, but in general these dwarf galaxies have some structure to them, with a well-defined core. Henize 2-10, as you can see, it a mess! It doesn’t have much overall structure, which is why it’s classified as an irregular galaxy. The thinking for big galaxies is that the black hole forms at the same time as the galaxy itself, and to regulate the growth of each other. When you look at lots of big galaxies, there’s a pretty clear overall correlation between the mass of the black hole and the galaxy around it.

So it’s pretty weird that Henize 2-10 has a supermassive black hole at all, but it turns out the hole is also about a million times the mass of the Sun — that’s pretty freakin’ big for such a tiny galaxy! That’s 1/4 the mass of our own black hole, in a galaxy that itself is far smaller than ours.

At the heart of most galaxies lies a supermassive black hole. And in some galaxies, the black hole is bigger and badder than usual. These raging overachievers, called active galactic nuclei, can be some of the brightest objects in space, sweeping up a huge amount of material from their local areas and emitting enough energy to outshine the galaxies around them. The question is, where do they get all the stuff to swallow? Not where scientists had expected, according to a new study.

An obvious answer—and the one that for years has seemed likeliest—is that these hyperactive black holes arise from the merger of galaxies. All the gas that comes together during a two-galaxy crash could feed a supermassive black hole, turning it from docile to brilliant. But there’s a problem.

“It’s totally intuitive,” said astrophysicist Knud Jahnke of the Max-Planck Institute for Astrophysics in Germany, a coauthor of the new study. “But it was a gut-feeling idea. In court you would say there was some circumstantial evidence for it, but no proof.” Earlier studies looked only at galaxies with the brightest active nuclei, which could have biased their results, Jahnke said. They also didn’t compare active galaxies to those with quiet black holes. [Wired]

For a study coming out in the Astrophysical Journal, Jahnke and others tried to put the galaxy merger hypotheses through a true controlled test, and they found no solid evidence to back it up.

You know those black holes the Large Hadron Collider was going to make and kill us all? Well, not only are we still here, but the LHC doesn’t seem to be making black holes at all—their decay signature is markedly absent from the data collected so far.

While that is good for those of us who want to keep living (we jest—the hypothetical micro black holes posed no danger), it’s also helping physicists make up their minds about how many dimensions there are in our universe. The lack of black holes at the LHC nullifies some of the wackier versions of string theory which depend on multiple dimensions.Read More

Those two purple lobes in the figure-eight shape are balloons of gamma ray energy that reach out 25,000 light years above and below the plane of the galaxy. Yet these huge structures have remained hidden from astronomers, until now.

Researchers do not yet know what produced the bubbles, but the fact that they appear to have relatively sharp edges suggests that they were produced in a single event. Finkbeiner said that would have required the rapid release of energy equivalent to about 100,000 supernovae, or exploding stars. One possibility is that there was a burst of star formation in the center of the galaxy producing massive, short-lived stars that exploded and ejected a great deal of gas and dust over a few million years. [Los Angeles Times]

It’s one of Stephen Hawking‘s most famous hypotheses (though one often co-credited to other researchers): According to the rules of quantum mechanics, a black hole—from which nothing should be able to escape—actually can emit material in the form of Hawking radiation. In the thirty-plus years since the reknowned physicist made his prediction Hawking radiation has remained theoretical, but a research team now claims to have seen it right in the lab.

Physicists have long realised that on the smallest scale, space is filled with a bubbling melee of particles leaping in and out of existence. These particles form as particle-antiparticle pairs and rapidly annihilate, returning their energy to the vacuum. Hawking’s prediction came from thinking about what might happen to particle pairs that form at the edge of a black hole. He realised that if one of the pair were to cross the event horizon, it could never return. But its partner on the other side would be free to go. [Technology Review]

The lonesome, unpaired particles streaming away would make it appear that the black hole was emitting radiation, Hawking argued.Read More

If you want to make a supermassive black hole quickly, collide young, massive proto-galaxies. After running the numbers on a supercomputer, that’s what researchers have recently concluded. Their simulation shows that a collision between massive gas clouds could make a black hole “from scratch” in a relatively short time.

Supermassive black hole truly are super massive–possibly billions of times the mass of our sun. They also appear to be super old; some estimates say they formed less than a billion years after the Big Bang. Thus the puzzle, how do you get so big so quickly?

The paper which appeared online yesterday in Nature (with associated letter) modeled the collision of two gas clouds that formed into a unstable gas disk, which channeled gas into its center. Eventually this dense center collapsed in on itself to make the black hole king. (See simulations of the proto-galaxies colliding, above.)

“It has been perplexing how such black holes with masses billions of times the mass of the sun could exist so early in the history of the universe,” astronomer Julie Comerford of University of California Berkeley, who was not involved in the study, wrote in an e-mail to Wired.com. “These simulations are an important advance in understanding how those supermassive black holes were built up so quickly.” [Wired]

I like the Milky Way. I dare say it’s my favorite galaxy, being home and all. But a blue star called HE 0437-5439 is in one big hurry to leave.

The star is zooming away from the Milky Way’s center at 16 million miles per hour, three times faster than our own sun glides across the galaxy. Astronomers had spotted the hasty traveler before—it’s one of 16 known “hypervelocity” stars. Now, with the help of the Hubble Space Telescope, Warren Brown of the Harvard-Smithsonian Center for Astrophysics traced the path of the star back to the event that allowed it to reach such great speed: a meeting with a black hole.

A hundred million years ago this star was one of three traveling together at a more sedate pace.

First, the orbiting pairs: Just about every galaxy has a supermassive black hole at its heart that is millions if not billions the size of our sun. Logic would suggest that when two galaxies merge, astronomers would see the two great black holes orbiting each other, but so far they’ve had tough luck, astronomer Julie Comerford says. “We expect the universe to be littered with these waltzing black holes,” Comerford said. “But until recently, only a few had ever been found.” Those missing black hole pairs posed problems for theories of how galaxies merge and grow [Wired.com].

Which came first: A galaxy or the supermassive black hole at its center? Thanks to a misfit quasar, astronomers have some new clues.

Quasars are particular kinds of black holes that release incredibly intense jets of energy, and scientists spied this one five billion light-years away. To their surprise, the astronomers found that unlike most quasars, this one was ”naked” and not situated at the centre of a galaxy. However, there was a companion galaxy close to it creating new stars at a frantic rate equivalent to about 350 suns per year [The Telegraph].